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1 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved. | |
2 // Use of this source code is governed by a BSD-style license that can be | |
3 // found in the LICENSE file. | |
4 | |
5 // Scopers help you manage ownership of a pointer, helping you easily manage the | |
6 // a pointer within a scope, and automatically destroying the pointer at the | |
7 // end of a scope. There are two main classes you will use, which coorespond | |
8 // to the operators new/delete and new[]/delete[]. | |
9 // | |
10 // Example usage (scoped_ptr): | |
11 // { | |
12 // scoped_ptr<Foo> foo(new Foo("wee")); | |
13 // } // foo goes out of scope, releasing the pointer with it. | |
14 // | |
15 // { | |
16 // scoped_ptr<Foo> foo; // No pointer managed. | |
17 // foo.reset(new Foo("wee")); // Now a pointer is managed. | |
18 // foo.reset(new Foo("wee2")); // Foo("wee") was destroyed. | |
19 // foo.reset(new Foo("wee3")); // Foo("wee2") was destroyed. | |
20 // foo->Method(); // Foo::Method() called. | |
21 // foo.get()->Method(); // Foo::Method() called. | |
22 // SomeFunc(foo.Release()); // SomeFunc takes owernship, foo no longer | |
23 // // manages a pointer. | |
24 // foo.reset(new Foo("wee4")); // foo manages a pointer again. | |
25 // foo.reset(); // Foo("wee4") destroyed, foo no longer | |
26 // // manages a pointer. | |
27 // } // foo wasn't managing a pointer, so nothing was destroyed. | |
28 // | |
29 // Example usage (scoped_array): | |
30 // { | |
31 // scoped_array<Foo> foo(new Foo[100]); | |
32 // foo.get()->Method(); // Foo::Method on the 0th element. | |
33 // foo[10].Method(); // Foo::Method on the 10th element. | |
34 // } | |
35 | |
36 #ifndef BASE_SCOPED_PTR_H_ | |
37 #define BASE_SCOPED_PTR_H_ | |
38 | |
39 // This is an implementation designed to match the anticipated future TR2 | |
40 // implementation of the scoped_ptr class, and its closely-related brethren, | |
41 // scoped_array, scoped_ptr_malloc. | |
42 | |
43 #include <assert.h> | |
44 #include <stdlib.h> | |
45 #include <cstddef> | |
46 | |
47 // A scoped_ptr<T> is like a T*, except that the destructor of scoped_ptr<T> | |
48 // automatically deletes the pointer it holds (if any). | |
49 // That is, scoped_ptr<T> owns the T object that it points to. | |
50 // Like a T*, a scoped_ptr<T> may hold either NULL or a pointer to a T object. | |
51 // Also like T*, scoped_ptr<T> is thread-compatible, and once you | |
52 // dereference it, you get the threadsafety guarantees of T. | |
53 // | |
54 // The size of a scoped_ptr is small: | |
55 // sizeof(scoped_ptr<C>) == sizeof(C*) | |
56 template <class C> | |
57 class scoped_ptr { | |
58 public: | |
59 | |
60 // The element type | |
61 typedef C element_type; | |
62 | |
63 // Constructor. Defaults to intializing with NULL. | |
64 // There is no way to create an uninitialized scoped_ptr. | |
65 // The input parameter must be allocated with new. | |
66 explicit scoped_ptr(C* p = NULL) : ptr_(p) { } | |
67 | |
68 // Destructor. If there is a C object, delete it. | |
69 // We don't need to test ptr_ == NULL because C++ does that for us. | |
70 ~scoped_ptr() { | |
71 enum { type_must_be_complete = sizeof(C) }; | |
72 delete ptr_; | |
73 } | |
74 | |
75 // Reset. Deletes the current owned object, if any. | |
76 // Then takes ownership of a new object, if given. | |
77 // this->reset(this->get()) works. | |
78 void reset(C* p = NULL) { | |
79 if (p != ptr_) { | |
80 enum { type_must_be_complete = sizeof(C) }; | |
81 delete ptr_; | |
82 ptr_ = p; | |
83 } | |
84 } | |
85 | |
86 // Accessors to get the owned object. | |
87 // operator* and operator-> will assert() if there is no current object. | |
88 C& operator*() const { | |
89 assert(ptr_ != NULL); | |
90 return *ptr_; | |
91 } | |
92 C* operator->() const { | |
93 assert(ptr_ != NULL); | |
94 return ptr_; | |
95 } | |
96 C* get() const { return ptr_; } | |
97 | |
98 // Comparison operators. | |
99 // These return whether two scoped_ptr refer to the same object, not just to | |
100 // two different but equal objects. | |
101 bool operator==(C* p) const { return ptr_ == p; } | |
102 bool operator!=(C* p) const { return ptr_ != p; } | |
103 | |
104 // Swap two scoped pointers. | |
105 void swap(scoped_ptr& p2) { | |
106 C* tmp = ptr_; | |
107 ptr_ = p2.ptr_; | |
108 p2.ptr_ = tmp; | |
109 } | |
110 | |
111 // Release a pointer. | |
112 // The return value is the current pointer held by this object. | |
113 // If this object holds a NULL pointer, the return value is NULL. | |
114 // After this operation, this object will hold a NULL pointer, | |
115 // and will not own the object any more. | |
116 C* release() { | |
117 C* retVal = ptr_; | |
118 ptr_ = NULL; | |
119 return retVal; | |
120 } | |
121 | |
122 private: | |
123 C* ptr_; | |
124 | |
125 // Forbid comparison of scoped_ptr types. If C2 != C, it totally doesn't | |
126 // make sense, and if C2 == C, it still doesn't make sense because you should | |
127 // never have the same object owned by two different scoped_ptrs. | |
128 template <class C2> bool operator==(scoped_ptr<C2> const& p2) const; | |
129 template <class C2> bool operator!=(scoped_ptr<C2> const& p2) const; | |
130 | |
131 // Disallow evil constructors | |
132 scoped_ptr(const scoped_ptr&); | |
133 void operator=(const scoped_ptr&); | |
134 }; | |
135 | |
136 // Free functions | |
137 template <class C> | |
138 void swap(scoped_ptr<C>& p1, scoped_ptr<C>& p2) { | |
139 p1.swap(p2); | |
140 } | |
141 | |
142 template <class C> | |
143 bool operator==(C* p1, const scoped_ptr<C>& p2) { | |
144 return p1 == p2.get(); | |
145 } | |
146 | |
147 template <class C> | |
148 bool operator!=(C* p1, const scoped_ptr<C>& p2) { | |
149 return p1 != p2.get(); | |
150 } | |
151 | |
152 // scoped_array<C> is like scoped_ptr<C>, except that the caller must allocate | |
153 // with new [] and the destructor deletes objects with delete []. | |
154 // | |
155 // As with scoped_ptr<C>, a scoped_array<C> either points to an object | |
156 // or is NULL. A scoped_array<C> owns the object that it points to. | |
157 // scoped_array<T> is thread-compatible, and once you index into it, | |
158 // the returned objects have only the threadsafety guarantees of T. | |
159 // | |
160 // Size: sizeof(scoped_array<C>) == sizeof(C*) | |
161 template <class C> | |
162 class scoped_array { | |
163 public: | |
164 | |
165 // The element type | |
166 typedef C element_type; | |
167 | |
168 // Constructor. Defaults to intializing with NULL. | |
169 // There is no way to create an uninitialized scoped_array. | |
170 // The input parameter must be allocated with new []. | |
171 explicit scoped_array(C* p = NULL) : array_(p) { } | |
172 | |
173 // Destructor. If there is a C object, delete it. | |
174 // We don't need to test ptr_ == NULL because C++ does that for us. | |
175 ~scoped_array() { | |
176 enum { type_must_be_complete = sizeof(C) }; | |
177 delete[] array_; | |
178 } | |
179 | |
180 // Reset. Deletes the current owned object, if any. | |
181 // Then takes ownership of a new object, if given. | |
182 // this->reset(this->get()) works. | |
183 void reset(C* p = NULL) { | |
184 if (p != array_) { | |
185 enum { type_must_be_complete = sizeof(C) }; | |
186 delete[] array_; | |
187 array_ = p; | |
188 } | |
189 } | |
190 | |
191 // Get one element of the current object. | |
192 // Will assert() if there is no current object, or index i is negative. | |
193 C& operator[](std::ptrdiff_t i) const { | |
194 assert(i >= 0); | |
195 assert(array_ != NULL); | |
196 return array_[i]; | |
197 } | |
198 | |
199 // Get a pointer to the zeroth element of the current object. | |
200 // If there is no current object, return NULL. | |
201 C* get() const { | |
202 return array_; | |
203 } | |
204 | |
205 // Comparison operators. | |
206 // These return whether two scoped_array refer to the same object, not just to | |
207 // two different but equal objects. | |
208 bool operator==(C* p) const { return array_ == p; } | |
209 bool operator!=(C* p) const { return array_ != p; } | |
210 | |
211 // Swap two scoped arrays. | |
212 void swap(scoped_array& p2) { | |
213 C* tmp = array_; | |
214 array_ = p2.array_; | |
215 p2.array_ = tmp; | |
216 } | |
217 | |
218 // Release an array. | |
219 // The return value is the current pointer held by this object. | |
220 // If this object holds a NULL pointer, the return value is NULL. | |
221 // After this operation, this object will hold a NULL pointer, | |
222 // and will not own the object any more. | |
223 C* release() { | |
224 C* retVal = array_; | |
225 array_ = NULL; | |
226 return retVal; | |
227 } | |
228 | |
229 private: | |
230 C* array_; | |
231 | |
232 // Forbid comparison of different scoped_array types. | |
233 template <class C2> bool operator==(scoped_array<C2> const& p2) const; | |
234 template <class C2> bool operator!=(scoped_array<C2> const& p2) const; | |
235 | |
236 // Disallow evil constructors | |
237 scoped_array(const scoped_array&); | |
238 void operator=(const scoped_array&); | |
239 }; | |
240 | |
241 // Free functions | |
242 template <class C> | |
243 void swap(scoped_array<C>& p1, scoped_array<C>& p2) { | |
244 p1.swap(p2); | |
245 } | |
246 | |
247 template <class C> | |
248 bool operator==(C* p1, const scoped_array<C>& p2) { | |
249 return p1 == p2.get(); | |
250 } | |
251 | |
252 template <class C> | |
253 bool operator!=(C* p1, const scoped_array<C>& p2) { | |
254 return p1 != p2.get(); | |
255 } | |
256 | |
257 // This class wraps the c library function free() in a class that can be | |
258 // passed as a template argument to scoped_ptr_malloc below. | |
259 class ScopedPtrMallocFree { | |
260 public: | |
261 inline void operator()(void* x) const { | |
262 free(x); | |
263 } | |
264 }; | |
265 | |
266 // scoped_ptr_malloc<> is similar to scoped_ptr<>, but it accepts a | |
267 // second template argument, the functor used to free the object. | |
268 | |
269 template<class C, class FreeProc = ScopedPtrMallocFree> | |
270 class scoped_ptr_malloc { | |
271 public: | |
272 | |
273 // The element type | |
274 typedef C element_type; | |
275 | |
276 // Constructor. Defaults to intializing with NULL. | |
277 // There is no way to create an uninitialized scoped_ptr. | |
278 // The input parameter must be allocated with an allocator that matches the | |
279 // Free functor. For the default Free functor, this is malloc, calloc, or | |
280 // realloc. | |
281 explicit scoped_ptr_malloc(C* p = NULL): ptr_(p) {} | |
282 | |
283 // Destructor. If there is a C object, call the Free functor. | |
284 ~scoped_ptr_malloc() { | |
285 free_(ptr_); | |
286 } | |
287 | |
288 // Reset. Calls the Free functor on the current owned object, if any. | |
289 // Then takes ownership of a new object, if given. | |
290 // this->reset(this->get()) works. | |
291 void reset(C* p = NULL) { | |
292 if (ptr_ != p) { | |
293 free_(ptr_); | |
294 ptr_ = p; | |
295 } | |
296 } | |
297 | |
298 // Get the current object. | |
299 // operator* and operator-> will cause an assert() failure if there is | |
300 // no current object. | |
301 C& operator*() const { | |
302 assert(ptr_ != NULL); | |
303 return *ptr_; | |
304 } | |
305 | |
306 C* operator->() const { | |
307 assert(ptr_ != NULL); | |
308 return ptr_; | |
309 } | |
310 | |
311 C* get() const { | |
312 return ptr_; | |
313 } | |
314 | |
315 // Comparison operators. | |
316 // These return whether a scoped_ptr_malloc and a plain pointer refer | |
317 // to the same object, not just to two different but equal objects. | |
318 // For compatibility wwith the boost-derived implementation, these | |
319 // take non-const arguments. | |
320 bool operator==(C* p) const { | |
321 return ptr_ == p; | |
322 } | |
323 | |
324 bool operator!=(C* p) const { | |
325 return ptr_ != p; | |
326 } | |
327 | |
328 // Swap two scoped pointers. | |
329 void swap(scoped_ptr_malloc & b) { | |
330 C* tmp = b.ptr_; | |
331 b.ptr_ = ptr_; | |
332 ptr_ = tmp; | |
333 } | |
334 | |
335 // Release a pointer. | |
336 // The return value is the current pointer held by this object. | |
337 // If this object holds a NULL pointer, the return value is NULL. | |
338 // After this operation, this object will hold a NULL pointer, | |
339 // and will not own the object any more. | |
340 C* release() { | |
341 C* tmp = ptr_; | |
342 ptr_ = NULL; | |
343 return tmp; | |
344 } | |
345 | |
346 private: | |
347 C* ptr_; | |
348 | |
349 // no reason to use these: each scoped_ptr_malloc should have its own object | |
350 template <class C2, class GP> | |
351 bool operator==(scoped_ptr_malloc<C2, GP> const& p) const; | |
352 template <class C2, class GP> | |
353 bool operator!=(scoped_ptr_malloc<C2, GP> const& p) const; | |
354 | |
355 static FreeProc const free_; | |
356 | |
357 // Disallow evil constructors | |
358 scoped_ptr_malloc(const scoped_ptr_malloc&); | |
359 void operator=(const scoped_ptr_malloc&); | |
360 }; | |
361 | |
362 template<class C, class FP> | |
363 FP const scoped_ptr_malloc<C, FP>::free_ = FP(); | |
364 | |
365 template<class C, class FP> inline | |
366 void swap(scoped_ptr_malloc<C, FP>& a, scoped_ptr_malloc<C, FP>& b) { | |
367 a.swap(b); | |
368 } | |
369 | |
370 template<class C, class FP> inline | |
371 bool operator==(C* p, const scoped_ptr_malloc<C, FP>& b) { | |
372 return p == b.get(); | |
373 } | |
374 | |
375 template<class C, class FP> inline | |
376 bool operator!=(C* p, const scoped_ptr_malloc<C, FP>& b) { | |
377 return p != b.get(); | |
378 } | |
379 | |
380 #endif // BASE_SCOPED_PTR_H_ | |
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